1. Field of the Invention
The present invention relates to a columnar structure such as a column member of a building structure or a bridge pier, an abutment, and the like of a bridge structure, and more particularly to an earthquake-resistant columnar structure in which earthquake resistance is imparted to the columnar structure and a method of reinforcing the earthquake resistance of a columnar structure.
2. Description of the Related Art
Conventionally, the following countermeasures for reinforcing earthquake resistance are generally adopted for buildings which lack aseismic performance so as to increase their earthquake resistance.
(1) Countermeasures for increasing the thickness of earthquake-resistant walls which lack wall thickness.
(2) Countermeasures for reinforcing columns such as by wrapping peripheries of the columns with steel plates, carbon fibers, or the like.
(3) Countermeasures for newly or additionally installing braces between two adjacent columns.
However, with these so-called earthquake-resistance increasing methods (1), (2), and (3), a large installation space is required to ensure sufficient earthquake resistance, while, on the other hand, the weight increases substantially due to the added members involved in the reinforcement, so that the above-described countermeasures do not necessarily improve the earthquake resistance effectively.
Meanwhile, in recent years, a base isolation method for absorbing vibrational energy consequent upon the shaking of a building by interposing so-called interlayer dampers between layers of the building has come to be adopted as an earthquake-resistant measure for buildings. The interlayer dampers used in this base isolation method include (a) a wall-like damper which makes use of the viscous shearing force and (b) a cylinder-like damper interposed between a PC wall or a brace and a column or a beam (a lead-extruded damper, an oil damper, and the like).
In contrast to the fact that the aforementioned countermeasures (1) to (3) counteract the seismic force by simply increasing the strength, this base isolation method is based on a dynamic design in which the response of a building is suppressed by absorbing the seismic energy intentionally, consequently reducing the seismic force acting on the columns and walls. Hence, the base isolation method is a rational and effective earthquake-resistant measure.
However, although the base isolation method using the interlayer dampers do not present a problem when the interlayer dampers are incorporated in advance at the time of newly constructing a building, the repair of wall members is unavoidable when the interlayer dampers are installed in an existing building. Hence, the problem of the installation space occurs in the same way as the aforementioned methods (1) to (3), and has been a bottleneck to the introduction of the base isolation method.
The present invention has been devised in view of the above-described circumstances, and its object is to overcome the problem of the installation space, which has been the bottleneck, without repairing the wall members in the introduction into an existing building of the base isolation method using the interlayer dampers exhibiting excellent vibration controlling characteristics
To this end, in the present invention, the above-described problem is resolved by adopting the new concept that the interlayer damper is fitted to a column member of a building. Another object of the present invention is to develop an interlayer damper which is fitted to a column member of a building.
Specifically, the following arrangements are adopted in the present invention:
Namely, in accordance with a first aspect of the invention, there is provided a columnar structure with earthquake resistance imparted thereto, the columnar structure having a polygonal cross section and adapted to support a load, comprising: a damping structural member attached to a side surface of the columnar structure, the damping structural member including a planarly rigid first plate member formed in the shape of a flat plate and having one end fixed to an upper portion of a columnar member and another end set as a free end, and a planarly rigid second plate member formed in the shape of a flat plate and having one end fixed to a lower portion of the columnar member and another end set as a free end, the first plate member and the second plate member being disposed in such a manner as to oppose each other with a predetermined interval therebetween, wherein a viscoelastic material capable of maintaining a solid shape is disposed between the first plate member and the second plate member, and is as a whole fixed to the first plate member and the second plate member.
In the above-described arrangement, as for the first plate member and the second plate member, either one of them may be disposed on an inner side, the other one disposed on an outer side, and the positions of the first plate member and the second plate member are not restricted. In addition, the upper portion of the columnar member referred to herein does not exclude a ceiling surface in the vicinity of an upper portion of the columnar member within a range in which the damping structural member exhibits an equivalent function. As for the lower portion of the columnar member as well, a floor surface is not excluded in the same way. It should be noted that the cross section of the columnar structure refers to a cross section formed by envelopes on its outer sides, and an H-type cross section belongs to a quadrangular shape.
In accordance with a second aspect of the invention, there is similarly provided a columnar structure comprising: a damping structural member attached to the columnar structure, the damping structural member including a planarly rigid plate member (resistance plate) formed in the shape of a flat plate and having an upper end fixed to an upper portion of a columnar member and a lower end set as a free end, and a casing formed in the shape of a rectangular box, the plate member being received in an inner space of the casing while maintaining an allowable movable range, a low end of the casing being fixed to a lower portion of the columnar member, wherein each of both surfaces of the plate member and each of both inner wall surfaces of the casing oppose each other with a very small interval therebetween, and a viscous material is filled in the casing.
In the above-described arrangement, the upper portion of the columnar member referred to herein does not exclude a ceiling surface in the vicinity of an upper portion of the columnar member within a range in which the damping structural member exhibits an equivalent function. As for the lower portion of the columnar member as well, a floor surface is not excluded in the same way. It should be noted that the cross section of the columnar structure refers to a cross section formed by envelopes on its outer sides, and an H-type cross section belongs to a quadrangular shape.
In accordance with a third aspect of the invention, there is similarly provided a columnar structure comprising: a damping structural member attached to the columnar structure, the damping structural member being arranged such that a planarly rigid plate member is disposed at a predetermined interval with a wall surface of a columnar member, and has one end fixed to one of an upper portion and a lower portion of the columnar member and another end set as a free end, and a viscoelastic material capable of maintaining a solid shape is disposed between the plate member and the wall surface of the columnar member, and is as a whole fixed to the plate member and the wall surface of the columnar member.
In the above-described arrangement, the upper portion of the columnar member referred to herein does not exclude a ceiling surface in the vicinity of an upper portion of the columnar member within a range in which the damping structural member exhibits an equivalent function. As for the lower portion of the columnar member as well, a floor surface is not excluded in the same way. It should be noted that the cross section of the columnar structure refers to a cross section formed by envelopes on its outer sides, and an H-type cross section belongs to a quadrangular shape.
In the above-described first, second, and third aspects of the invention, as for the columnar structure, a column member of a building structure or a bridge pier and an abutment of a bridge structure are directly used as objects, but other columnar members are not to be excluded.
In addition, although a quadrangular columnar member is normally used as the columnar member, the columnar member may be triangular or another polygon having five or more sides and angles. Further, (1) whether the damping structural members are disposed on all of the four sides of the quadrangular column, (2) whether the damping structural members are disposed on two mutually opposing surfaces thereof, and (3) whether the damping structural members are disposed on two mutually adjacent surfaces thereof are selective matters.
In accordance with a fourth aspect of the invention, there is provided a method of reinforcing the earthquake resistance of a columnar structure, comprising the step of: attaching the damping structural member according to the first aspect of the invention to a side surface of the columnar structure so as to impart earthquake resistance to the columnar structure having a polygonal cross section and adapted to support a load.
In accordance with a fifth aspect of the invention, there is similarly provided a method of reinforcing the earthquake resistance of a columnar structure, comprising the step of: attaching the damping structural member according to the second aspect of the invention to a side surface of the columnar structure so as to impart earthquake resistance to the columnar structure having a polygonal cross section and adapted to support a load.
In accordance with a sixth aspect of the invention, there is similarly provided a method of reinforcing the earthquake resistance of a columnar structure, comprising the step of: attaching the damping structural member according to the third aspect of the invention to a side surface of the columnar structure so as to impart earthquake resistance to the columnar structure having a polygonal cross section and adapted to support a load.
(Operation)
In accordance with the first aspect of the invention, when the columnar member is subjected to bending deformation by receiving a forced vibrational force such as earthquake motion, the first plate member and the second plate member undergo relative displacements with respect to each other, and the damping viscoelastic material placed therebetween undergoes shearing deformation, so that the damping viscoelastic material absorbs the displacements by virtue of its internal damping capacity.
In accordance with the second aspect of the invention, when the columnar member is subjected to bending deformation by receiving a forced vibrational force such as earthquake motion, the plate member and the casing undergo relative displacements with respect to each other, and viscous shear resisting force is produced by the viscous material interposed between the plate surfaces of the two members. Hence, the drag is transmitted to the upper portion of the columnar member by the plate members, and is transmitted to the lower portion of the columnar member by the casing, thereby absorbing the seismic oscillations.
In accordance with the third aspect of the invention, when the columnar member is subjected to bending deformation by receiving a forced vibrational force such as earthquake motion, relative displacement occurs between the columnar member and the plate member, and the damping viscoelastic material placed therebetween undergoes shearing deformation, so that the damping viscoelastic material absorbs the displacement by virtue of its internal damping capacity.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings.